Stave cooling device employing double-tubes

ABSTRACT

A stave cooling device wherein a double-drawn-steel-tube is cast into a main-body of castable metal, the outer surface of the outer tube of said double-tube being closely welded to said main body and the inner tube of said double-tube serving as the passage of the coolant.

United States Patent Saiga et a1.

STAVE COOLING DEVICE EMPLOYING DOUBLE-TUBES Inventors: Yoshinori Saiga, Funabashi; Kazunori Mohri, Yokahama, both of Japan Assignee: .lshikawajima-Harima Jukogyo Kabushiki Kaisha, Tokyo-to, Japan Filed: June 4, 1971 Appl. No.: 150,216

Foreign Application Priority Data June 4, 1970 Japan ..4s/54403 U.S. Cl. ..l65/70, 165/134, 165/168,

165/180, 266/32, 263/44 Int. Cl ..F28f 7/02, C2lb 7/10 Field of Search 165/70, 168, 171, 180, 134, 165/81; 266/32; 122/6; 263/44 [451 Dec. 19, 1972 [56] References Cited UNITED STATES PATENTS 1,090,574 3/1904 Shannon ..266/32 X 2,743,089 4/1956 Gardner et a1 ..l65/7O X Primary Examiner-Albert W. Davis, Jr.

' Attorney-Nolte and Nolte [57] ABSTRACT A stave cooling device wherein a double-drawn-steeltube is cast into a main-body of castable metal, the outer surface of the outer tube of said double-tube being closely welded to said main body and the inner tube of said double-tube serving as the passage of the coolant.

1 Claim, 2 Drawing Figures PKTENTED I97? 3. 706, 343

FIG/ F/GZ IN VE NTORS YOSHINOR/ SAIGA KAZUNORI MOHRI BY 7% i M ATTORNEYS STAVE COOLING DEVICE EMPLOYING DOUBLE- TUBES DETAILED EXPLANATION OF INVENTION Various methods or systems have been known for cooling the blast furnaces. The present invention relates especially to a method or system for cooling staves of the blast furnaces, and employs the double-tubes made by drawing steel (which will be referred to as double-drawn-steel-tubes for brevity in this translation) which are inserted or placed in the staves when they are cast in order to improve the cooling efficiency.

More particularly the present invention relatesto a stave cooling device employing double-tubes characterized by double-drawn-steel-tubes inserted or placed in a main body of cast-steel, cast-iron or other castable metal when said main body is cast, in such a manner that both ends of said double-tube may extend out of consequence the coolant leaks into the furnace. Furthermore when the cooling tube is inserted or placed into the stave when it is cast, carbon in the caststeel or -iron diffuses into the cooling tube so that the surface of the tube is cemented. Therefore the mechanical strength as well as ductility of the cooling tube are somewhat lowered so that the cracks can more easily propagate.

To prevent the cracks of the cooling tube, it must not be welded to the cast-steel or -iron, but when there is a space between the cast -steel or -iron and the cooling tube, the thermal conductivity or heat transfer between them is extremely lowered. Therefore the cooling effect is lowered accordingly.

The present invention gives the solution to the above defects and problems encountered in the prior art, and will become more apparent from the following description of the preferred embodiment thereof taken in consaid main body, the outer surface of the outer tube of j i i h h acgompanying drawing;

said double-tube being closely welded to said main body when it is cast, and the inner tube of said doubletube serving as the passage of the coolant.

The object of the invention is to provide a stave cooling device which has a high cooling efficiency and prevents the leakage of the coolant into the furnace even when the main bodies of the staves are cracked by the thermal stress, fatigue, shock and the like.

In general the prior art stave cooling devices are such that steel tubes are inserted into the staves when the latter are cast in order to pass the coolant such as cooling water or saturated water, whereby the heat received on the heat-receiving surfaces of the staves may be removed by the coolant. In this operation, the thermal conductivity or heat transfer between the cast-steel of the main body of the stave and the tube is an important factor determining the cooling efficiency. Therefore when the thermal conductivityor heat transfer is maintained at a highest degree, effective cooling may be attained. Therefore, it is required to weld the steel tube to the stave into a unitary construction in order to attain the highest degree of the thermal conductivity or heat transfer between said main body of the stave and the cooling tube. However, the following problems or defects are brought about. The cast-steel or -iron which constitutes the main body of the stave is generally subjected to high temperature in the furnace for a long time and repeatedly subjected to continuous and sudden temperature variation due to ever-changing conditions in the furnace. Therefore the thermal stress is produced because of the temperature gradient between the heat-receiving surface of the stave subjected to high temperature in the furnace and the inner surface of the cooling tube which is in contact with the coolant. Furthermore the main body is subjected to high temperature for a long time so that the structure of the cast-steel or -iron changes partially so that the volume of the stave main body varies. In consequence internal stress is generated. In addition the main body is subjected to fatigue because of the continuous temperature variation. Furthermore the main body is subjected to thermal shock because of the sudden temperature variation. Therefore, cracks are produced in the caststeel or -iron of the stave main body, and when the cracks propagate through the stave main body, the cooling tube is also cracked because the tube is welded to the cast-steel or-iron of the stave main body. As a FIG. 1 is a front view, partly broken, of one explanatory embodiment of the present invention; and

FIG. 2 is a longitudinal sectional view thereof taken along the line A-A of FIG. 1.

A. stave generally comprises a main body a made of cast-steel or -iron. According to the invention a doubledrawn-steel-tube consisting of an outer tube b and an inner tube 0, both of which are inserted or placed in the main body a when it is cast. In this casting both of the ends 1 and 2 of the double-drawn-steel-tube are extended out of the main body a, and the outer surface of the outer tube b is welded to the main body a so as to be constructed as a unit. The coolant used in the operation of the blast furnace, then flows through the inner tube c in the direction indicated by the arrows 3 and 4 so that the heat received by the heat-receiving surface 5 of the main body may be dissipated.

The present invention employs a double-drawn-steeltube which has a sufficient strength. The inner and outer tubes 0 and b are mechanically closely in contact with each other. The outer surface of the outer tube b is integrally welded to the main body a by these expedients the thermal conduction is better and the cooling efficiency is much improved. In addition, even when the cracks of the main body caused by thermal stress, fatigue, shock and the like are propagated into the outer tube b, the propagation is stopped at the interface between the outer and inner tubes b and c. In other words, the cracks will not propagate into the inner tube c so that the coolant in the tube c will not leak into the furnace. Even when the outer tube b should become fragile by cementation and the like during casting operation, the inner tube c is left intact and has a sufficiently high mechanical strength.

The cooling system of the present invention is simple in construction and reliable in operation and has many advantageous effects hitherto unattained by the prior art.

What is claimed is:

1. A stave cooling device employing double-tubes comprising a double-drawn-steel-tube inserted in a main body a of cast-steel, cast-iron or castable metal when said main body is cast, in such a manner that both ends (1) and (2) of said double-tube may extend out of said main body (a), the outer surface of the outer tube (b) of said double-tube being closely welded to said l060ll 0183 main body a when it is cast and the inner tube c of said double-tube serving as the passage of the coolant. 

1. A stave cooling device employing double-tubes comprising a double-drawn-steel-tube inserted in a main body a of cast-steel, cast-iron or castable metal when said main body is cast, in such a manner that both ends (1) and (2) of said double-tube may extend out of said main body (a), the outer surface of the outer tube (b) of said double-tube being closely welded to said main body a when it is cast and the inner tube c of said double-tube serving as the passage of the coolant. 